Methods, Network Function Nodes and Computer Readable Media for Event Subscription Management

ABSTRACT

The present disclosure provides methods for event subscription management in a network comprising a set of NF nodes, and corresponding NF nodes. The method comprises receiving a subscription request of an event for a user from an event subscriber, in response to receipt of the subscription request, transmitting, to a second network function node, a query request for querying whether the event for the user has been subscribed; and if a response to the query request from the second network function node indicates that the event for the user has been subscribed, transmitting, to the second network function node, an updating request for updating a subscriber list of the event for the user by the second network function node to include the event subscriber into the subscriber list. The present disclosure further discloses a corresponding method which comprises receiving a query request from a first network function node for querying whether an event for a user has been subscribed, in response to reception of the query request, checking whether an indicator indicating the event for the user has been subscribed has been set, and transmitting a check result to the first network function node. The present disclosure further provides corresponding computer readable medium.

TECHNICAL FIELD

The present disclosure generally relates to the technical field oftelecommunication, and particularly to methods and Network Function (NF)nodes for event subscription management in a network comprising a set ofNF nodes and corresponding computer readable media.

BACKGROUND

This section is intended to provide a background to the variousembodiments of the technology described in this disclosure. Thedescription in this section may include concepts that could be pursued,but are not necessarily ones that have been previously conceived orpursued. Therefore, unless otherwise indicated herein, what is describedin this section is not prior art to the description and/or claims ofthis disclosure and is not admitted to be prior art by the mereinclusion in this section.

In Fifth Generation (5G) networks, a Network Slice is introduced as alogical network that provides specific network capabilities and networkcharacteristics. An instance of a network slice (e.g. a network sliceinstance, NSI) is a set of Network Function (NF) instances and therequired resources (e.g., compute, storage, and networking resources)which form a deployed Network Slice. An NF is a 3GPP adopted or 3GPPdefined processing function in a network, which has defined functionalbehavior and 3GPP defined interfaces. An NF can be implemented either asa network element on dedicated hardware, a software instance running ona dedicated hardware, or as a virtualized functional instantiated on anappropriate platform, e.g., on a cloud infrastructure.

Among the NFs, a UDM (Unified Data Management) is defined, whichfunctions to manage subscription from other NFs in the network. As perservice definition in 3GPP 29.502, the following service has beendefined:

-   -   Nudm_EventExposure: this service allows NF consumers to        subscribe to receive an event, and provide monitoring indication        of the event to the subscribed NF consumers.

For a 5G system to be deployed, it is common that there are multiple UDMinstances providing same services.

It can be seen so far, only standalone event subscription management isdefined, which is inefficient when there are multiple NF instancesproviding same services and might even cause an error.

SUMMARY

At least some objects of the present disclosure are to provide technicalsolutions capable of improving efficiency of event subscription whenthere are multiple NF instances providing same services.

According to one aspect of the present disclosure, there is provided amethod implemented at a first network function node for managing eventsubscription. The method comprises receiving a subscription request ofan event for a user from an event subscriber, in response to receipt ofthe subscription request, transmitting, to a second network functionnode, a query request for querying whether the event for the user hasbeen subscribed; and if a response to the query request from the secondnetwork function node indicates that the event for the user has beensubscribed, transmitting, to the second network function node, anupdating request for updating a subscriber list of the event for theuser by the second network function node to include the event subscriberinto the subscriber list.

In an exemplary embodiment, if the response to the query requestindicates that the event for the user has not been subscribed, themethod further comprises initiating subscription of the event for theuser with a serving node and transmitting a creating request withidentification information of the event subscriber for creating thesubscriber list for the event of the user and including the eventsubscriber in the created subscriber list by the second network node.

In an exemplary embodiment, the first network function node is one of aUnified Data Management (UDM), a Network Exposure Function (NEF), and anAccess and Mobility Management Function (AMF).

In an exemplary embodiment, the second network function node is aUnified Data Repository (UDR).

According to another aspect of the present disclosure, there is provideda method implemented at a second network function node for managingevent subscription. The method comprises receiving a query request froma first network function node for querying whether an event for a userhas been subscribed, in response to reception of the query request,checking whether an indicator indicating the event for the user has beensubscribed has been set, and transmitting a check result to the firstnetwork function node.

In an exemplary embodiment, the method further comprises receiving anupdating request for updating a subscriber list of the event for theuser with an event subscriber to the event from the first networkfunction node, and in response to reception of the updating request,updating a subscriber list of the event for the user to include theevent subscriber.

In an exemplary embodiment, the method further comprises receiving acreating request with identification information of the event subscriberto subscribe the event for the user from the first network functionnode, in response to reception of the creating request, setting theindicator, and creating the subscriber list of the event for the userand including the event subscriber into the subscriber list of the eventfor the user.

In an exemplary embodiment, the indicator is set in a table stored inthe second network function node that describes event subscription ofthe user.

In an exemplary embodiment, the subscriber list is created in a tablestored in the second network function node that describes subscriptionof the event for the user.

In an exemplary embodiment, the first network function node is one of aUnified Data Management (UDM), a Network Exposure Function (NEF), and anAccess and Mobility Management Function (AMF).

In an exemplary embodiment, the second network function node is aUnified Data Repository (UDR).

According to another aspect of the present disclosure, there is provideda method implemented at a first network function node for managing eventun-subscription. The method comprises receiving an un-subscriptionrequest of an event for a user from an event subscriber to un-subscribethe event, in response to reception of the un-subscription request,transmitting, to a second network function node, a query request forquerying whether the event subscriber is a last subscriber for the eventof the user in a subscriber list of the event for the user, and if aresponse to the query request from the second network function nodeindicates that the event subscriber is not the last subscriber for theevent of the user, transmitting a removing request to the second networkfunction node, for removing, by the second network function node, theevent subscriber from the subscriber list of the event for the user.

In an exemplary embodiment, the removing request includes identificationinformation of the event subscriber.

In an exemplary embodiment, if the response to the query requestindicates that the event subscriber is the last subscriber for the eventof the user, the method further comprises transmitting an event removingrequest to the second network function node for removing the subscriberlist by the second network function node; and initiating un-subscriptionof the event for the user with a serving node.

According to another aspect of the present disclosure, there is provideda method implemented at a second network function node for managingevent un-subscription. The method comprises receiving a query requestfor an event subscriber to un-subscribe an event for a user, from afirst network function node for querying whether the event subscriber isa last subscriber for the event of the user in a subscriber list of theevent for the user, in response to reception of the query request,checking whether the event subscriber is the last subscriber in thesubscriber list of the event for the user, and transmitting a checkresult to the first network function node.

In an exemplary embodiment, the method further comprises receiving aremoving request from the first network function node for removing theevent subscriber from the subscriber list of the event for the user, andin response to reception of the removing request, removing the eventsubscriber from the subscriber list of the event for the user.

In an exemplary embodiment, the removing request includes identificationinformation of the event subscriber to un-subscribe the event.

In an exemplary embodiment, the method further comprises receiving anevent removing request for removing the subscriber list from the firstnetwork function node, and in response to reception of the eventremoving request, removing the subscriber list of the event for theuser.

In an exemplary embodiment, the method further comprises removing anindicator indicating the event of the user has been subscribed.

In an exemplary embodiment, the removing the subscriber list comprisesremoving the subscriber list from a table stored in the second networkfunction node that describes subscription of the event for the user.

In an exemplary embodiment, the removing the indicator comprisesremoving the indicator from a table stored in the second networkfunction node that describes event subscription of the user.

According to another aspect of the present disclosure, a first NF nodeis provided, comprising: a communication interface arranged forcommunication, at least one processor, and a memory comprisinginstructions which, when executed by the at least one processor, causethe first NF node to receive a subscription request of an event for auser from an event subscriber, in response to receipt of thesubscription request, transmit, to a second network function node, aquery request for querying whether the event for the user has beensubscribed; and if a response to the query request from the secondnetwork function node indicates that the event for the user has beensubscribed, transmit, to the second network function node, an updatingrequest for updating a subscriber list of the event for the user by thesecond network function node to include the event subscriber into thesubscriber list.

According to another aspect of the present disclosure, a second NF nodeis provided, comprising: a communication interface arranged forcommunication, at least one processor, and a memory comprisinginstructions which, when executed by the at least one processor, causethe second NF node to receive a query request from a first networkfunction node for querying whether an event for a user has beensubscribed, in response to reception of the query request, check whetheran indicator indicating the event for the user has been subscribed hasbeen set, and transmit a check result to the first network functionnode.

According to another aspect of the present disclosure, a first NF nodeis provided, comprising: a communication interface arranged forcommunication, at least one processor, and a memory comprisinginstructions which, when executed by the at least one processor, causethe first NF node to receive an un-subscription request of an event fora user from an event subscriber, in response to reception of theun-subscription request, transmit, to a second network function node, aquery request for querying whether the event subscriber is a lastsubscriber for the event of the user in a subscriber list of the eventfor the user; and if a response to the query request from the secondnetwork function node indicates that the event subscriber is not thelast subscriber for the event of the user, transmit a removing requestto the second network function node, for removing, by the second networkfunction node, the event subscriber from the subscriber list of theevent for the user.

According to another aspect of the present disclosure, a second NF nodeis provided, comprising: a communication interface arranged forcommunication, at least one processor, and a memory comprisinginstructions which, when executed by the at least one processor, causethe second NF node to receive a query request for an event subscriber toun-subscribe an event for a user, from a first network function node forquerying whether the event subscriber is a last subscriber for the eventof the user in a subscriber list of the event for the user, in responseto reception of the query request, check whether the event subscriber isthe last subscriber in the subscriber list of the event for the user,and transmit a check result to the first network function node.

According to another aspect of the present disclosure, a computerreadable medium which stores computer program comprising instructionswhich, when executed on at least one processor, cause the at least oneprocessor to perform the methods for event subscription management asdiscussed previously.

According to the above technical solutions of the present disclosure, onone hand, when a subscription for an event of a user is raised from anevent subscriber, it firstly checks whether the event of the user hasbeen subscribed. If the event of the user has not been subscribed, asubscription process is initiated. If the event of the user has beensubscribed previously and has not been un-subscribed yet, the eventsubscriber is added in a subscriber list and no subscription processwill be initiated. Accordingly, redundant subscription process for thesame event of the same user will be avoided. On the other hand, when aun-subscription for an event of a user is raised from an eventsubscriber, it firstly checks whether the event subscriber is the lastsubscriber for the event of the user. If it is, a un-subscriptionprocess is initiated. If the event subscriber is not the last subscriberfor the event of the user, the event subscriber is removed from thesubscriber list and no un-subscription process will be initiated.Accordingly, the un-subscription from one event subscriber will notaffect the other event subscribers that are interested in the event ofthe user.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects, advantages and characteristics of the present disclosurewill be more apparent, according to descriptions of preferredembodiments in connection with the drawings, on which:

FIG. 1 illustrates one example of a wireless communication system inwhich embodiments of the present disclosure may be implemented;

FIG. 2 illustrates a wireless communication system represented as a 5Gnetwork architecture composed of core NFs;

FIG. 3 illustrates a 5G network architecture using service-basedinterfaces between the NFs in the control plane, instead of thepoint-to-point reference points/interfaces used in the 5G networkarchitecture of FIG. 2;

FIG. 4 illustrates a data storage architecture in a 5G network;

FIG. 5 illustratively shows a flowchart of a method for managing eventsubscription according to an exemplary embodiment of the presentdisclosure;

FIG. 6 illustratively shows a flowchart of a method for managing eventsubscription according to an exemplary embodiment of the presentdisclosure;

FIG. 7 shows an exemplifying signaling diagram illustrating details ofthe methods schematically illustrated in FIGS. 5 and 6;

FIG. 8 illustratively shows a flowchart of a method for managing eventun-subscription according to an exemplary embodiment of the presentdisclosure;

FIG. 9 illustratively shows a flowchart of a method for managing eventun-subscription according to an exemplary embodiment of the presentdisclosure;

FIG. 10 shows an exemplifying signaling diagram illustrating details ofthe methods schematically illustrated in FIGS. 8 and 9;

FIG. 11 illustratively shows a schematic structure diagram of a first NFnode according to an exemplary embodiment of the present disclosure;

FIG. 12 illustratively shows a schematic structure diagram of a first NFnode according to an exemplary embodiment of the present disclosure;

FIG. 13 illustratively shows a schematic structure diagram of a secondNF node according to an exemplary embodiment of the present disclosure;and

FIG. 14 illustratively shows a schematic structure diagram of a secondNF node according to an exemplary embodiment of the present disclosure.

It should be noted that throughout the drawings, same or similarreference numbers are used for indicating same or similar elements;various parts in the drawings are not drawn to scale, but only for anillustrative purpose, and thus should not be understood as anylimitations and constraints on the scope of the present disclosure.

DETAILED DESCRIPTION

Hereinafter, the principle and spirit of the present disclosure will bedescribed with reference to illustrative embodiments. Some of theembodiments contemplated herein will now be described more fully withreference to the accompanying drawings. Other embodiments, however, arecontained within the scope of the subject matter disclosed herein, thedisclosed subject matter should not be construed as limited to only theembodiments set forth herein; rather, these embodiments are provided byway of example to convey the scope of the subject matter to thoseskilled in the art. Additional information may also be found inreferences as follows:

-   -   1) 3GPP 23.501, V15.3.0, (2018-09)    -   2) 3GPP 23.502, V15.3.0 (2018-09)    -   3) 3GPP 29.503, V15.1.0 (2018-09), and    -   4) 3GPP 29.505, V15.1.0 (2018-09).

References in this specification to “one embodiment,” “an embodiment,”“an example embodiment,” etc. indicate that the embodiment described mayinclude a particular feature, structure, or characteristic, but it isnot necessary that every embodiment includes the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of theskilled in the art to affect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be liming of exemplaryembodiments. As used herein, the singular forms “a”, “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises”, “comprising”, “has”, “having”, “includes” and/or“including”, when used herein, specify the presence of stated features,elements, and/or components etc., but do not preclude the presence oraddition of one or more other features, elements, components and/orcombinations thereof.

In the following description and claims, unless defined otherwise, alltechnical and scientific terms used herein have the same meaning ascommonly understood by one of ordinary skills in the art to which thisdisclosure belongs.

The techniques described herein may be used for various wirelesscommunication networks such as Code Division Multiple Access (CDMA),Time Division Multiple Access (TDMA), Frequency Division Multiple Access(FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), SingleCarrier-Frequency Division Multiple Access (SC-FDMA), Long TermEvolution (LTE) and other networks developed in the future. The terms“network” and “system” are sometimes used interchangeably. Forillustration only, certain aspects of the techniques are described belowfor the next, i.e. the 5^(th) generation of wireless communicationnetwork. However, it will be appreciated by the skilled in the art thatthe techniques described herein may also be used for other wirelessnetworks such as LTE and corresponding radio technologies mentionedherein as well as wireless networks and radio technologies proposed inthe future.

As used herein, the term “UE” may be, by way of example and notlimitation, a User Equipment (UE), a SS (Subscriber Station), a PortableSubscriber Station (PSS), a Mobile Station (MS), a Mobile Terminal (MT)or an Access Terminal (AT). The UE may include, but not limited to,mobile phones, cellular phones, smart phones, or personal digitalassistants (PDAs), portable computers, image capture terminal devicessuch as digital cameras, gaming terminal devices, music storage andplayback appliances, wearable terminal devices, vehicle-mounted wirelessterminal devices and the like. In the following description, the terms“UE”, “terminal device”, “mobile terminal” and “user equipment” may beused interchangeably.

FIG. 1 illustrates one example of a wireless communication system 100 inwhich embodiments of the present disclosure may be implemented. Thewireless communication system 100 may be a cellular communicationssystem such as, for example, a 5G New Radio (NR) network or an LTEcellular communications system. As illustrated, in this example, thewireless communication system 100 includes a plurality of radio accessnodes 120 (e.g., evolved Node B:s (eNBs), 5G base stations which arereferred to as gNBs, or other base stations or similar) and a pluralityof wireless communication devices 140 (e.g., conventional UEs, MachineType Communication (MTC)/Machine-to-Machine (M2M) UEs). The wirelesscommunication system 100 is organized into cells 160, which areconnected to a core network 180 via the corresponding radio access nodes120. The radio access nodes 120 are capable of communicating with thewireless communication devices 140 (also referred to herein ascommunication device 140 or UEs 140) along with any additional elementssuitable to support communication between wireless communication devicesor between a wireless communication device and another communicationdevice (such as a landline telephone). The core network 180 includes oneor more network node(s) or function(s) 210. In some embodiments, thenetwork nodes/functions 210 may comprise, for example, any of thenetwork functions shown in FIGS. 2-3.

FIG. 2 illustrates a wireless communication system 200 represented as a5G network architecture composed of core NFs, where interaction betweenany two NFs is represented by a point-to-point referencepoint/interface.

Seen from the access side the 5G network architecture shown in FIG. 2comprises a plurality of User Equipment (UEs) connected to either aRadio Access Network (RAN) or an Access Network (AN) as well as anAccess and Mobility Management Function (AMF). Typically, the R(AN)comprises base stations, e.g. such as evolved Node Bs (eNBs) or 5G basestations (gNBs) or similar. Seen from the core network side, the 5G coreNFs shown in FIG. 2 include a Network Slice Selection Function (NSSF),an Authentication Server Function (AUSF), a Unified Data Management(UDM), an Access and Mobility Management Function (AMF), a SessionManagement Function (SMF), a Policy Control Function (PCF), anApplication Function (AF).

Reference point representations of the 5G network architecture are usedto develop detailed call flows in the normative standardization. The N1reference point is defined to carry signaling between UE and AMF. Thereference points for connecting between AN and AMF and between AN andUPF are defined as N2 and N3, respectively. There is a reference point,N11, between AMF and SMF, which implies that SMF is at least partlycontrolled by AMF. N4 is used by SMF and UPF so that the UPF can be setusing the control signal generated by the SMF, and the UPF can reportits state to the SMF. N9 is the reference point for the connectionbetween different UPFs, and N14 is the reference point connectingbetween different AMFs, respectively. N15 and N7 are defined since PCFapplies policy to AMF and SMP, respectively. N12 is required for the AMFto perform authentication of the UE. N8 and N10 are defined because thesubscription data of UE is required for AMF and SMF.

The 5G core network aims at separating user plane and control plane. Theuser plane carries user traffic while the control plane carriessignaling in the network. In FIG. 2, the UPF is in the user plane andall other NFs, i.e., AMF, SMF, PCF, AF, AUSF, and UDM, are in thecontrol plane. Separating the user and control planes guarantees eachplane resource to be scaled independently. It also allows UPFs to bedeployed separately from control plane functions in a distributedfashion. In this architecture, UPFs may be deployed very close to UEs toshorten the Round Trip Time (RTT) between UEs and data network for someapplications requiring low latency.

The core 5G network architecture is composed of modularized functions.For example, the AMF and SMF are independent functions in the controlplane. Separated AMF and SMF allow independent evolution and scaling.Other control plane functions like PCF and AUSF can be separated asshown in FIG. 2. Modularized function design enables the 5G core networkto support various services flexibly.

Each NF interacts with another NF directly. It is possible to useintermediate functions to route messages from one NF to another NF. Inthe control plane, a set of interactions between two NFs is defined as aservice so that its reuse is possible. This service enables support formodularity. The user plane supports interactions such as forwardingoperations between different UPFs.

FIG. 3 illustrates a 5G network architecture using service-basedinterfaces between the NFs in the control plane, instead of thepoint-to-point reference points/interfaces used in the 5G networkarchitecture of FIG. 2. However, the NFs described above with referenceto FIG. 2 correspond to the NFs shown in FIG. 3. The service(s) etc.that a NF provides to other authorized NFs can be exposed to theauthorized NFs through the service-based interface. In FIG. 3 theservice based interfaces are indicated by the letter “N” followed by thename of the NF, e.g. Namf for the service based interface of the AMF andNsmf for the service based interface of the SMF etc. The NetworkExposure Function (NEF) and the Network Function Repository Function(NRF) in FIG. 3 are not shown in FIG. 2 discussed above. However, itshould be clarified that all NFs depicted in FIG. 2 can interact withthe NEF and the NRF of FIG. 3 as necessary, though not explicitlyindicated in FIG. 2.

Some properties of the NFs shown in FIGS. 2-3 may be described in thefollowing manner. The AMF provides UE-based authentication,authorization, mobility management, etc. A UE even using multiple accesstechnologies is basically connected to a single AMF because the AMF isindependent of the access technologies. The SMF is responsible forsession management and allocates IP addresses to UEs. It also selectsand controls the UPF for data transfer. If a UE has multiple sessions,different SMFs may be allocated to each session to manage themindividually and possibly provide different functionalities per session.The AF provides information on the packet flow to PCF responsible forpolicy control in order to support Quality of Service (QoS). Based onthe information, PCF determines policies about mobility and sessionmanagement to make AMF and SMF operate properly. The AUSF supportsauthentication function for UEs or similar and thus stores data forauthentication of UEs or similar while UDM stores subscription data ofUE. The Data Network (DN), not part of the 5G core network, providesInternet access or operator services and similar.

FIG. 4 illustrates a data storage architecture in a 5G network. Therecan be multiple UDRs (Unified Data Repository) deployed in the network,each of which can accommodate different data sets or subsets (e.g.subscription data, subscription policy data, data for exposure,application data) and/or serve different sets of NFs. Deployments wherea UDR serves a single NF and stores its data, and, thus, can beintegrated with this NF, may be possible.

The Nudr interface is defined for the network functions (i.e. NF ServiceConsumers), such as UDM, PCF and NEF, to access a particular set of thedata stored and to read, update (including add, modify), delete, andsubscribe to notification of relevant data changes in the UDR.

Each NF Service Consumer accessing the UDR, via Nudr, shall be able toadd, modify, update or delete only the data it is authorized to change.This authorization shall be performed by the UDR on a per data set andNF service consumer basis and potentially on a per UE, subscriptiongranularity.

An NF may be implemented either as a network element on a dedicatedhardware, as a software instance running on a dedicated hardware, or asa virtualized function instantiated on an appropriate platform, e.g., acloud infrastructure.

As 3GPP 29.503 defined, for the Nudm_EventExposure service the followingservice operations are defined:

-   -   Subscribe    -   Unsubscribe    -   Notify

The Nudm_EventExposure service is used by consumer NFs (e.g. NEF) tosubscribe to notifications of event occurrence by means of the Subscribeservice operation. For events that can be detected by the AMF, the UDMmakes use of the appropriate AMF service operation to subscribe onbehalf of the consumer NF (e.g. NEF).

The Nudm_EventExposure service is also used by the consumer NFs (e.g.NEF) that have previously subscribed to notifications, to unsubscribe bymeans of the Unsubscribe service operation. For events that can bedetected by the AMF, the UDM makes use of the appropriate AMF serviceoperation to unsubscribe on behalf of the consumer NF (e.g. NEF).

The Nudm_EventExposure service is also used by the subscribed consumerNFs (e.g. NEF) to get notified by the UDM when a subscribed event occursat the UDM by means of the Notify service operation. For subscribedevents that can occur at the AMF, the consumer NF (e.g. NEF) makes useof the corresponding AMF service operation to get notified by the AMFdirectly without UDM involvement.

For the related AMF context data model (shared by UDR), it is defined inthe following table (defined in 3GPP 29.503).

TABLE 1 Definition of type Amf3GppAccessRegistration Attribute name Datatype P Cardinality Description amfInstanceId NfInstanceId M 1 Theidentity the AMF uses to register in the NRF. supportedFeaturesSupportedFeatures O 0 . . . 1 See subclause 6.2.8 purgeFlag PurgeFlag O0 . . . 1 This flag indicates whether or not the AMF has deregistered.It shall not be included in the Registration service operation. pei PeiO 0 . . . 1 Permanent Equipment Identifier. imsVoPS ImsVoPS O 0 . . . 1Indicates per UE if “IMS Voice over PS Sessions” is homogeneouslysupported in all TAs in the serving AMF, or homogeneously not supported,or if support is non-homogeneous/unknown. Absence of this attributeshall be interpreted as “non homogenous or unknown” support.deregCallbackUri Uri M 1 A URI provided by the AMF to receive(implicitly subscribed) notifications on deregistration.pcscfRestorationCallbackUri Uri O 0 . . . 1 A URI provided by the AMF toreceive (implicitly subscribed) notifications on the need for P-CSCFRestoration. guami Guami C 0 . . . 1 This IE shall contain the servingAMF's GUAMI. It shall be included if the NF service consumer is an AMF.backupAmfInfo array(BackupAmfInfo) C 0 . . . N This IE shall be includedif the NF service consumer is an AMF and the AMF supports the AMFmanagement without UDSF for the first interaction with UDM. The UDM usesthis attribute to do an NRF query in order to invoke later services in abackup AMF, e.g. Namf_EventExposure. Optional attributes of this typethat are also attributes of the derived typeAmf3GppAccessRegistrationModification (see clause 6.2.6.2.7) shall notbe marked with “nullable: true” in the OpenAPI file.

For the related event subscription data models (shared by UDR), they aredefined in following 3 tables (defined in 3GPP 29.503):

TABLE 2 Definition of type EeSubscription Attribute name Data type PCardinality Description callbackReference Uri M 1 URI provided by the NFservice consumer to receive notifications monitoringConfigurationmap(MonitoringConfiguration) M 1 . . . N A map (list of key-value pairswhere referenceId converted from integer to string serves as key) ofMonitoringConfigurations; see subclause 6.4.6.2.3 reportingOptionsReportingOptions O 0 . . . 1 This IE may be included if the NF serviceconsumer wants to describe how the reports of the event to be generated.supportedFeatures SupportedFeatures O 0 . . . 1 See subclause 6.4.8

TABLE 3 Definition of type MonitoringConfiguration Attribute name Datatype P Cardinality Description referenceId ReferenceId M 1 Reference Iduniquely identifies the Monitoring Configuration eventType EventType M 1String; see subclause 6.4.6.3.3 immediateFlag boolean O 0 . . . 1Indicates if an immediate event report in the subscription responseindicating current value/ status of the event is required or not. If theflag is not present then immediate reporting shall not be done.

TABLE 4 Enumeration EventType Enumeration value Description“LOSS_OF_CONNECTIVITY” Loss of connectivity “UE_REACHABILITY_FOR_DATA”UE reachability for data “UE_REACHABILITY_FOR_SMS” UE reachability forSMS “LOCATION_REPORTING” Location Reporting“CHANGE_OF_SUPI_PEI_ASSOCIATION” Change of SUPI-PEI association“ROAMING_STATUS” Roaming Status “COMMUNICATION_FAILURE” CommunicationFailure “AVAILABILITY_AFTER_DNN_FAILURE” Availability after DNN failure

For the related created event subscription data model (shared by UDR),it is defined in following table (defined in 3GPP 29.503):

TABLE 5 Definition of type CreatedEeSubscription Attribute name Datatype P Cardinality Description eeSubscription EeSubscription M 1 This IEshall contain the representation of the created event subscription.numberOfUes Uinteger C 0 . . . 1 This IE shall be included if the eventsubscription is for a group of UEs. When present, this IE shallrepresent the number of UEs in the group. eventtReportsarray(MonitoringReport) O 0 . . . N This IE when present, shall containthe status of events that are requested for immediate reporting as well,if those events are available at the time of subscription.

It is obvious that there are events which are commonly interested bymultiple NFs, such as the UE reachability for SMS event, but such commonevents are not managed efficiently. Currently only standalone eventsubscription management is defined. When there are multiple NFs who areinterested on the same event, for example the reachability for SMS forthe same user, the standalone event management is not efficient or evenworse it is erroneous.

Hereinafter, a method for event subscription management in a networkcomprising a set of NF nodes according to an exemplary embodiment of thepresent disclosure will be described with reference to FIGS. 5 and 6.

FIG. 5 illustratively shows a flowchart of a method 500 for managingevent subscription according to an exemplary embodiment of the presentdisclosure. In an embodiment, the method 500 may be performed at a firstnetwork function node.

As shown in FIG. 5, the method 500 may include Steps S510-S530.

In Step S510, a subscription request of an event for a user is receivedfrom an event subscriber. In response to the receipt of the subscriptionrequest, the method proceeds to step S520, in which the first networkfunction node transmits, to a second network function node, a queryrequest for querying whether the event for the user has been subscribed.The first network function node receives a response to the query requestfrom the second network function node at step S530. An example of StepS510, S520 and S530 is Step S702, S704 and S708 shown in FIG. 7.

If the response to the query request from the second network functionnode indicates that the event for the user has been subscribed, themethod proceeds to step S540, in which the first network function nodetransmits, to the second network function node, an updating request forupdating a subscriber list of the event for the user by the secondnetwork function node to include the event subscriber into thesubscriber list. The updating request may include identificationinformation of the event subscriber. An example of Step S540 is StepS726 shown in FIG. 7.

If the response to the query request from the second network functionnode indicates that the event for the user has not been subscribed, themethod proceeds to step S550, in which the first network function nodesinitiates subscription of the event for the user with a serving node,and in step S560, the first network function nodes transmits a creatingrequest with identification information of the event subscriber forcreating the subscriber list for the event of the user and including theevent subscriber in the created subscriber list by the second networknode. An example of Step S550, S560 is Step S710 and S714 shown in FIG.7.

Please note that the terms “updating request” and “creating request” asused above are named for differentiating the two requests but not forlimiting the meaning or scope of the description reciting these terms.

In an exemplary embodiment of the present disclosure, the first networkfunction node may be one of a Unified Data Management (UDM), a NetworkExposure Function (NEF), and an Access and Mobility Management Function(AMF).

In an exemplary embodiment of the present disclosure, the second networkfunction node is a Unified Data Repository (UDR).

According to the embodiment of the present disclosure, the first networkfunction node, when receiving a subscription request of an event for auser, checks with the second network function node whether there isalready subscription for the event of the user. If there is no suchsubscription, the first network function node will transmit a request,for example a creating request, with identification information of theevent subscriber to the second network function node, which will recordthe subscription of the event for the user. The first network functionnode will then initiate the subscription of the event. For example, thefirst network function node may determine which network function node inthe network to perform the event monitoring, i.e., the serving node, andthen transmit the subscription request to the serving node to performthe event. Thereafter, when the first network function node receives asubscription request for the same event of the same user, after checkingwith the second network function node, the first network function nodeknows that there is already subscription for the event of the user. Thefirst network function node will then transmit a request, for example anupdating request to the second network function node, which will recordthe event subscriber as a subscriber for the event of the user. Therequest may include identification information of the event subscriber.At this time, the first network function node will not initiate thesubscription of the event to the serving node again because the eventhas been subscribed. The event subscriber will be provided with anotification of the event because it has been added in the subscriberlist for the event. According to the embodiment of the presentdisclosure, un-necessary duplicated subscription towards the servingnode can be avoided.

FIG. 6 illustratively shows a flowchart of a method 600 for managingevent subscription according to an exemplary embodiment of the presentdisclosure. In an embodiment, the method 600 may be performed at asecond network function node.

As shown in FIG. 6, the method 600 may include Steps S610-S630.

In Step S610, the second network function node receives a query requestfrom a first network function node for querying whether an event for auser has been subscribed. In response to reception of the query request,the method proceeds to step S620, in which the second network functionnode checks whether an indicator indicating the event for the user hasbeen subscribed has been set. Then, the method proceeds to step S630, inwhich the second network function node transmits a check result to thefirst network function node. An example of Step S610, S620 and S630 isStep S704, S706 and S708 shown in FIG. 7.

In response to the transmission of the check result to the first networkfunction node, the method 600 may also include Step S640, in which thesecond network function node may receive, from the first networkfunction node, an updating request for updating a subscriber list of theevent for the user with an event subscriber to the event. The updatingrequest may include identification information of the event subscriber.In response to reception of the updating request, the method proceeds tostep S650, in which the second network function node updates asubscriber list of the event for the user to include the eventsubscriber. An example of Step S640 and S650 is Step S726 and S728 shownin FIG. 7.

The method 600 may also include step S660, in which the second networkfunction node may receive, from the first network function node, acreating request with identification information of the event subscriberto subscribe the event for the user. In response to reception of thecreating request, the method proceeds to step S670, in which the secondnetwork function node sets the indicator. In step S680, the secondnetwork function node creates the subscriber list of the event for theuser and includes the event subscriber into the subscriber list of theevent for the user. An example of Step S660, S670 and S680 is Step S714and S716 shown in FIG. 7. Please note that the steps in FIG. 6 areexemplified in the order as shown. Some steps such as S670 and S680 maybe performed in a different order, e.g. in parallel or in a reverseorder.

In an exemplary embodiment of the present disclosure, the indicator isset in a table stored in the second network function node that describesevent subscription of the user.

In an exemplary embodiment of the present disclosure, the subscriberlist is created in a table stored in the second network function nodethat describes subscription of the event for the user.

In an exemplary embodiment of the present disclosure, the first networkfunction node is one of a Unified Data Management (UDM), a NetworkExposure Function (NEF), and an Access and Mobility Management Function(AMF).

In an exemplary embodiment of the present disclosure, the second networkfunction node is a Unified Data Repository (UDR).

According to the embodiment of the present disclosure, the secondnetwork function node, when receiving a query request from a firstnetwork function node for querying whether an event for a user has beensubscribed, determines whether there is already subscription for theevent of the user by checking whether an indicator indicating the eventfor the user has been subscribed has been set. The second networkfunction transmits its check result to the first network function node.If the indicator has not been set, the second network function nodeknows that there is no subscription for the event of the user and willsend the check result to the first network function node indicating thatthe event for that user has not been subscribed. Accordingly, the firstnetwork function node will transmit a request, for example a creatingrequest, with identification information of the event subscriber to thesecond network function node. Upon receiving the creating request, thesecond network function node sets the indicator and creates a subscriberlist of the event for the user and includes the event subscriber intothe subscriber list of the event for the user. Thereafter, when thesecond network function node receives a query request for queryingwhether the event for the user has been subscribed, it determines thatthere is already subscription for the event of the user with the setindicator and will indicate, e.g. with a check result, to the firstnetwork function node that the event for the user has been subscribed.The first network function node thereby knows that there is alreadysubscription for the event of the user. The first network function nodewill then transmit a request, for example an updating request to thesecond network function node. The request may include identificationinformation of the event subscriber. Upon receiving the updatingrequest, the second network function node updates the subscriber list ofthe event for the user to include the event subscriber. According to theembodiment of the present disclosure, an indicator is introduced toindicate whether an event for a user has been subscribed or not, and asubscriber list is introduced to maintain a list of subscribers for thesame event of the user. By looking into the indicator, it is knownwhether the event has been subscribed, and thus un-necessary duplicatedsubscription to the serving node can be avoided.

FIG. 7 shows an exemplifying signaling diagram 700 illustrating detailsof the methods schematically illustrated in FIGS. 5 and 6.

The example shown in FIG. 7 involves a UE 701, an AMF 703, a list ofUDMs 705, a UDR 707 and a list of NFs 709. It is shown that the list ofUDMs 705 includes two UDM instances, UDM1 and UDM2, and the list of NF709 includes two NF instances, NF1 and NF2. It is only an example andthe present disclosure is not limited thereto.

When NF1 initiates UE reachability subscription for a certain user(Subscriber Permanent Identity (SUPI)=xxx), one of UDM instance such asUDM1 is selected based on load balancing rules. UDM1 receives thereachability subscription from NF1 (S702).

UDM1 transmits a query request to UDR 707 (S704) for querying whetherthe event for the user has been subscribed.

UDR 707 then checks whether the event for the user has been subscribed(S706). In the example, it is assumed that the event for the user hasnot been subscribed.

UDR 707 then transmits its check result to UDM1 (S708).

Upon receiving the response from UDR 707 indicating the event for theuser has not been subscribed, UDM1 then initiates the reachabilitysubscription to the serving node, in this case it is AMF 703 (S710). AMF703 starts monitoring of UE reachability (S712).

Upon reception of acknowledgement that the reachability subscription issuccessful, UDM1 transmits a creating request to UDR 707 (S714) alongwith identity of NF1, which is the event subscriber.

Upon receiving the creating request, UDR 707 sets UE reachabilitysubscription indicator (e.g., =true) for the user and creates asubscriber list to include NF1 (S716).

When NF2 initiates UE reachability subscription for the same user(SUPI=xxx), one of UDM instance such as UDM2 may be selected based onload balancing rules. UDM2 receives the reachability subscription fromNF2 (S718).

UDM2 transmits a query request to UDR 707 (S720) for querying whetherthe event for the user has been subscribed.

UDR 707 then checks whether the event for the user has been subscribed(S722). At the time, UDR 707 finds that the UE reachability subscriptionindicator is set to be true, and then transmits the check resultindicating the event has been subscribed to UDM2 (S724).

UDM2 then knows that the reachability event for the same user has beensubscribed before, and then transmits an updating request to UDR 707(S726).

Upon receiving the updating request, UDR 707 updates the subscriber listto include NF2 (S728).

At the time, UDM 705 will not initiate the reachability subscription toAMF.

Therefore, un-necessary duplicated un-necessary reachabilitysubscription towards the serving node can be avoided.

The UE reachability subscription indicator can be added in for example,Amf3GppAccessRegistration. Below is an example of theAmf3GppAccessRegistration modified according to the present disclosure,where the field in bold is an example of UE reachability subscriptionindicator.

TABLE 6 Definition of type Amf3GppAccessRegistration Attribute name Datatype P Cardinality Description amfInstanceId NfInstanceId M 1 Theidentity the AMF uses to register in the NRF. supportedFeaturesSupportedFeatures O 0 . . . 1 See subclause 6.2.8 purgeFlag PurgeFlag O0 . . . 1 This flag indicates whether or not the AMF has deregistered.It shall not be included in the Registration service operation. pei PeiO 0 . . . 1 Permanent Equipment Identifier. imsVoPS ImsVoPS O 0 . . . 1Indicates per UE if “IMS Voice over PS Sessions” is homogeneouslysupported in all TAs in the serving AMF, or homogeneously not supported,or if support is non-homogeneous/unknown. Absence of this attributeshall be interpreted as “non homogenous or unknown” support.deregCallbackUri Uri M 1 A URI provided by the AMF to receive(implicitly subscribed) notifications on deregistration.pcscfRestorationCallbackUri Uri O 0 . . . 1 A URI provided by the AMF toreceive (implicitly subscribed) notifications on the need for P-CSCFRestoration. guami Guami C 0 . . . 1 This IE shall contain the servingAMF's GUAMI. It shall be included if the NF service consumer is an AMF.backupAmfInfo array(BackupAmfInfo) C 0 . . . N This IE shall be includedif the NF service consumer is an AMF and the AMF supports the AMFmanagement without UDSF for the first interaction with UDM. The UDM usesthis attribute to do an NRF query in order to invoke later services in abackup AMF, e.g. Namf_EventExposure. urrpIndicator boolean O 0 . . . 1This IE indicates whether UE reachability for this user has beensubscribed or not: True: Reachability event for this user has beensubscribed False: Reachability event for this user has not beensubscribed yet or although has been subscribed before but now it isun-subscribed Optional attributes of this type that are also attributesof the derived type Amf3GppAccessRegistrationModification (see clause6.2.6.2.7) shall not be marked with “nullable: true” in the OpenAPIfile.

The subscriber list can be added in for example, CreatedEeSubscription.Below is an example of the Amf3GppAccessRegistratio modified accordingto the present disclosure, where the field in bold is an example of thesubscriber list.

TABLE 7 Definition of type CreatedEeSubscription Attribute name Datatype P Cardinality Description eeSubscription EeSubscription M 1 This IEshall contain the representation of the created event subscription.numberOfUes Uinteger C 0 . . . 1 This IE shall be includ This IE shallcontain the representation of the created event subscription.ed if theevent subscription is for a group of Ues. When present, this IE shallrepresent the number of Ues in the group. eventtReportsarray(MonitoringReport) O 0 . . . N This IE when present, shall containthe status of events that are requested for immediate reporting as well,if those events are available at the time of subscription. eeSubscribersArray O 1 . . . N This IE shall contain the event subscriber list(NfInstanceId) of the created common event subscription.

The UE reachability is given as an example event to be subscribed inFIG. 7. The event in the present disclosure is not limited to thereto.As another example, the event may be any of those listed in Table 4.

FIG. 8 illustratively shows a flowchart of a method 800 for managingevent un-subscription according to an exemplary embodiment of thepresent disclosure. In an embodiment, the method 800 may be performed ata first network function node.

As shown in FIG. 8, the method 800 may include Steps S810˜S830.

In Step S810, an un-subscription request of an event for a user isreceived from an event subscriber to un-subscribe the event. In responseto the receipt of the subscription request, the method proceeds to stepS820, in which the first network function node transmits, to a secondnetwork function node, a query request for querying whether the eventsubscriber is a last subscriber for the event of the user in asubscriber list of the event for the user. The query request may includeidentification information of the event subscriber. In response to thequerying, the first network function node receives a response to thequery request from the second network function node at step S830. Anexample of Step S810, S820 and S830 is Step S1002, S1004 and S1008 shownin FIG. 10.

If the response to the query request from the second network functionnode indicates that the event subscriber is not the last subscriber forthe event of the user, the method proceeds to step S840, in which thefirst network function node transmits, to the second network functionnode, a removing request for removing, by the second network functionnode, the event subscriber from the subscriber list of the event for theuser. In an exemplary embodiment of the present disclosure, the removingrequest may include identification information of the event subscriber.An example of Step S840 is Step S1010 shown in FIG. 10.

If the response to the query request from the second network functionnode indicates that the event subscriber is the last subscriber for theevent of the user, the method proceeds to step S850, in which the firstnetwork function node initiates un-subscription of the event for theuser with a serving node. If the un-subscription of the event for theuser with a serving node is successful, then at step S860, the firstnetwork function node transmits, to the second network function node, anevent removing request for removing the subscriber list by the secondnetwork function node. An example of Step S850 and S860 is Step S1022and S1026 shown in FIG. 10.

Please note that the terms “removing request” and “event removingrequest” as used above are named for differentiating the two requestsbut not for additionally limiting the meaning or scope of thedescription reciting these terms.

In an exemplary embodiment of the present disclosure, the first networkfunction node may be one of a Unified Data Management (UDM), a NetworkExposure Function (NEF), and an Access and Mobility Management Function(AMF).

In an exemplary embodiment of the present disclosure, the second networkfunction node is a Unified Data Repository (UDR).

According to the embodiment of the present disclosure, the first networkfunction node, when receiving a un-subscription request of an event fora user from an event subscriber, checks with the second network functionnode whether the event subscriber is the last subscriber for the eventof the user. If the event subscriber is not the last subscriber for theevent of the user, the first network function node will transmit arequest, for example a removing request, with identification informationof the event subscriber to the second network function node, which willremove the event subscriber from the subscriber list of the event forthe user. At that time, the first network function node knows that thereis still at least one event subscriber for the event of the user sincethat requesting event subscriber is not the last one, and so noun-subscription of the event for the user with a serving node will beinitiated. Thereafter, when the first network function node receives aun-subscription request of an event for a user from an event subscriber,it checks with the second network function node whether the eventsubscriber is the last subscriber for the event of the user. If theevent subscriber is the last subscriber for the event of the user, thefirst network function node will transmit a request, for example anevent removing request, to the second network function node, which willremove the subscriber list of the event for the user. At that time, thefirst network function node knows that there is no more event subscriberfor the event of the user since that requesting event subscriber is thelast one, and so it initiates un-subscription of the event for the userwith a serving node to un-subscribe the event. According to theembodiment of the present disclosure, un-subscription of an event from aspecific event subscriber doesn't impact the subscription of the sameevent by others. It is just a removal of the event subscriber from thesubscriber list. Only when it is the last one in the subscriber list, anun-subscription of the event is transmitted to the serving node.

FIG. 9 illustratively shows a flowchart of a method 900 for managingevent un-subscription according to an exemplary embodiment of thepresent disclosure. In an embodiment, the method 900 may be performed ata second network function node.

As shown in FIG. 9, the method 900 may include Steps S910-S930.

In Step S910, the second network function node receives a query requestfor an event subscriber to un-subscribe an event for a user, from afirst network function node for querying whether the event subscriber isa last subscriber for the event of the user in a subscriber list of theevent for the user. The query request may include identificationinformation of the event subscriber. In response to reception of thequery request, the method proceeds to step S920, in which the secondnetwork function node checks whether the event subscriber is the lastsubscriber in the subscriber list of the event for the user. Then, themethod proceeds to step S930, in which the second network function nodetransmits a check result to the first network function node. An exampleof Step S910, S920 and S930 is Step S1002, S1006 and S1008 shown in FIG.10.

In response to the transmission of the check result to the first networkfunction node, the method 900 may also include Step S940, in which thesecond network function node receives a removing request from the firstnetwork function node for removing the event subscriber from thesubscriber list of the event for the user. In response to reception ofthe removing request, the method proceeds to step S950, in which thesecond network function node removes the event subscriber from thesubscriber list of the event for the user. In an exemplary embodiment ofthe present disclosure, the removing request may include identificationinformation of the event subscriber to un-subscribe the event. Anexample of Step S940 and S950 is Step S1010 and S1012 shown in FIG. 10.

The method 900 may also include step S960, in which the second networkfunction node receives an event removing request for removing thesubscriber list from the first network function node. In response toreception of the event removing request, the method proceeds to stepS970, in which the second network function node removes the subscriberlist of the event for the user, and in step S980, the second networkfunction node removes an indicator indicating the event of the user hasbeen subscribed. Please note that the steps in FIG. 9 are exemplified inthe order as shown. Some steps such as S970 and S980 may be performed ina different order, e.g. in parallel or in a reverse order. An example ofStep S960, S970 and S980 is Step S1026 and S1028 shown in FIG. 10.

In an exemplary embodiment of the present disclosure, the step S970 ofremoving the subscriber list comprises removing the subscriber list froma table stored in the second network function node that describessubscription of the event for the user.

In an exemplary embodiment of the present disclosure, the step S980 ofremoving the indicator comprises removing the indicator from a tablestored in the second network function node that describes eventsubscription of the user.

In an exemplary embodiment of the present disclosure, the first networkfunction node is one of a Unified Data Management (UDM), a NetworkExposure Function (NEF), and an Access and Mobility Management Function(AMF).

In an exemplary embodiment of the present disclosure, the second networkfunction node is a Unified Data Repository (UDR).

According to the embodiment of the present disclosure, the secondnetwork function node, when receiving a query request from a firstnetwork function node for querying whether the event subscriber is alast subscriber for the event of the user in a subscriber list of theevent for the user, looks into the subscriber list of the event for theuser to determine whether the event subscriber is a last subscriber forthe event of the user. The second network function then transmits itscheck result to the first network function node. If the event subscriberis not the last subscriber for the event of the user, the first networkfunction node will transmit a request, for example a removing request,with identification information of the event subscriber to the secondnetwork function node. Upon receiving the removing request, the secondnetwork function node will remove the event subscriber from thesubscriber list of the event for the user. At that time, the firstnetwork function node knows that there is still at least one eventsubscriber for the event of the user since that requesting eventsubscriber is not the last one, and so no un-subscription of the eventfor the user with a serving node will be initiated. Thereafter, when thesecond network function node receives a query request from a firstnetwork function node for querying whether the event subscriber is alast subscriber for the event of the user in a subscriber list of theevent for the user, it looks into the subscriber list of the event forthe user to determine whether the event subscriber is a last subscriberfor the event of the user. The second network function then transmitsits check result to the first network function node. If the eventsubscriber is the last subscriber for the event of the user, the firstnetwork function node will transmit a request, for example an eventremoving request, to the second network function node. Upon receivingthe event removing request, the second network function node will removethe subscriber list of the event for the user. At that time, the firstnetwork function node knows that there is no more event subscriber forthe event of the user since that requesting event subscriber is the lastone, and so it initiates un-subscription of the event for the user witha serving node to un-subscribe the event. According to the embodiment ofthe present disclosure, un-subscription of an event from a specificevent subscriber doesn't impact the subscription of the same event byothers. It is just a removal of the event subscriber from the subscriberlist. Only when it is the last one in the subscriber list, anun-subscription of the event is transmitted to the serving node.

FIG. 10 shows an exemplifying signaling diagram 1000 illustratingdetails of the methods schematically illustrated in FIGS. 8 and 9.

The example shown in FIG. 10 involves a UE 1001, an AMF 1003, a list ofUDMs 1005, a UDR 1007 and a list of NF 1009. It is shown that the listof UDMs 1005 includes two UDM, UDM1 and UDM2, and the list of NF 1009includes two NF, NF1 and NF2. It is only an example and the presentdisclosure is not limited thereto.

When NF1 initiates un-subscription of UE reachability for a certain user(SUPI=xxx), one of UDM instance such as UDM1 is selected based on e.g.,load balancing rules. UDM1 receives the reachability un-subscriptionfrom NF1 (S1002).

UDM1 transmits a query request to UDR 1007 (S1004) for querying whetherNF1 is the last subscriber for the reachability of the user.

UDR 1007 then checks whether NF1 is the last subscriber for thereachability of the user (S1006). In the example, it is assumed that theNF1 and NF2 have subscribed for the UE reachability of the user.Therefore, NF1 is not the last for the reachability of the user.

UDR 1007 then transmits its check result to UDM1 (S1008).

Upon receiving the response from UDR 1007 indicating NF1 is not the lastsubscriber for the reachability of the user, UDM1 transmits a removingrequest to UDR 1007 (S1010) along with identity of NF1, which is theevent subscriber that requests to un-subscribe the reachability.

Upon receiving the removing request, UDR 1007 removes NF1 from thesubscriber list (S1012). In the example, now only NF2 is left in thesubscriber list.

At the time, UDM 1005 will not initiate the reachability un-subscriptionto a serving node that provides notification on the UE reachability,i.e., AMF 1003 in the example. AMF 1003 continues monitoring UEreachability since NF2 subscribes the event.

When NF2 initiates UE reachability un-subscription for the same user(SUPI=xxx), one of UDM instance such as UDM2 is selected based on e.g.,load balancing rules. UDM2 receives the reachability un-subscriptionfrom NF2 (S1014).

UDM2 transmits a query request to UDR 1007 (S1016) for querying whetherNF2 is the last subscriber for the reachability of the user.

UDR 1007 then checks whether NF2 is the last subscriber for thereachability of the user (S1018). In the example, NF2 is the last forthe reachability of the user.

UDR 1007 then transmits its check result to UDM1 (S1020).

Upon receiving the response from UDR 1007 indicating NF2 is the lastsubscriber for the reachability of the user, UDM1 initiates thereachability un-subscription to the serving node, in this case it is AMF1003 (S1022). AMF 1003 stops monitoring of UE reachability of the user(S1024).

Upon reception of acknowledgement of the un-subscription is successful,UDM1 transmits an event removing request to UDR 1007 (S1026).

Upon receiving the event removing request, UDR 1007 removes thesubscriber list and an indicator indicating the reachability of the userhas been subscribed (S1028).

Hereinafter, a structure of a first NF node will be described withreference to FIG. 11. FIG. 11 illustratively shows a schematic structurediagram of a first NF node 1100 (e.g. UDM 705 as shown in FIG. 7 and/orUDM 1007 as shown in FIG. 10, as described previously) according to anexemplary embodiment of the present disclosure. The first NF node 1100in FIG. 11 may perform the method 500 for event subscription managementdescribed previously with reference to FIG. 5 and/or the method 800 forevent un-subscription management described previously with reference toFIG. 8. Accordingly, some detailed description on the first NF node 1100may refer to the corresponding description of the method 500 for eventsubscription management and/or the corresponding description of themethod 800 for event un-subscription management as previously discussed.

As shown in FIG. 11, the first NF node 1100 may include a receivingmodule 1101, a determining module 1102, a subscription managing module1103 and a transmitting module 1104. As will be understood by theskilled in the art, common components in the first NF node 1100 areomitted in FIG. 11 for not obscuring the idea of the present disclosure.Also, some modules may be distributed in more modules or integrated intofewer modules. For example, the receiving module 1101 and thetransmitting module 1104 may be integrated into a transceiver module.

In an exemplary embodiment of the present disclosure, the receivingmodule 1101 of the first NF node 1100 may be configured to receive asubscription request of an event for a user from an event subscriber.The transmitting module 1104 of the first NF node 1100 may be configuredto transmit, in response to receipt of the subscription request, a queryrequest for querying whether the event for the user has been subscribedto a second network function node. The receiving module 1101 of thefirst NF node 1100 may be configured to receive a response to the queryrequest from the second network function node. The determining module1102 of the first NF node 1100 may be configured to determine whetherthe event for the user has been subscribed based on the response. If itis determined that the event for the user has been subscribed, thetransmitting module 1104 of the first NF node 1100 may be configured totransmit an updating request to the second network function node. Theupdating request may include identification information of the eventsubscriber. If it is determined that the event for the user has not beensubscribed, the transmitting module 1104 of the first NF node 1100 maybe configured to transmit, to the second network function node, acreating request with identification information of the event subscriberfor creating the subscriber list for the event of the user, and thesubscription managing module 1103 of the first NF node 1100 may beconfigured to initiate subscription of the event for the user with aserving node.

In another exemplary embodiment of the present disclosure, the receivingmodule 1101 of the first NF node 1100 may be further configured toreceive an un-subscription request of an event for a user from an eventsubscriber. The transmitting module 1104 of the first NF node 1100 maybe configured to transmit to a second network function node, in responseto receipt of the un-subscription request, a query request for queryingwhether the event subscriber is a last subscriber for the event of theuser in a subscriber list of the event for the user. The query requestmay include identification information of the event subscriber. Thereceiving module 1101 of the first NF node 1100 may be configured toreceive a response to the query request from the second network functionnode. The determining module 1102 of the first NF node 1100 may beconfigured to determine whether the event subscriber is not the lastsubscriber based on the response. If it is determined that the eventsubscriber is not the last subscriber, the transmitting module 1104 ofthe first NF node 1100 may be configured to transmit, to the secondnetwork function node, a removing request for removing, by the secondnetwork function node, the event subscriber from the subscriber list ofthe event for the user. If it is determined that the event subscriber isthe last subscriber for the event of the user, the transmitting module1104 of the first NF node 1100 may be configured to transmit, to thesecond network function node, an event removing request to the secondnetwork function node for removing the subscriber list by the secondnetwork function node, and the subscription managing module 1103 of thefirst NF node 1100 may be configured to initiate un-subscription of theevent for the user with a serving node.

In an exemplary embodiment of the present disclosure, the first networkfunction node is one of a Unified Data Management (UDM), a NetworkExposure Function (NEF), and an Access and Mobility Management Function(AMF). In an exemplary embodiment of the present disclosure, the secondnetwork function node is a Unified Data Repository (UDR).

Hereinafter, another structure of a first NF node 1200 will be describedwith reference to FIG. 12. FIG. 12 illustratively shows a schematicstructure diagram of a first NF node 1200 (e.g., UDM 705 as shown inFIG. 7 and/or UDM 1005 as shown in FIG. 10, as described previously)according to an exemplary embodiment of the present disclosure. Thefirst NF node 1200 in FIG. 12 may perform the method 500 for eventsubscription management described previously with reference to FIG. 5and/or the method 800 for event un-subscription management describedpreviously with reference to FIG. 8. Accordingly, some detaileddescription on the first NF node 1200 may refer to the correspondingdescription of the method 500 for event subscription management and/orthe corresponding description of the method 800 for eventun-subscription management as previously discussed.

As shown in FIG. 12, the first NF node 1200 may include at least onecontroller or processor 1203 including e.g., any suitable CentralProcessing Unit, CPU, microcontroller, Digital Signal Processor, DSP,etc., capable of executing computer program instructions. The computerprogram instructions may be stored in a memory 1205. The memory 1205 maybe any combination of a RAM (Random Access Memory) and a ROM (Read OnlyMemory). The memory may also comprise persistent storage, which, forexample, can be any single one or combination of magnetic memory,optical memory, or solid state memory or even remotely mounted memory.The exemplary first NF node 1200 further comprises a communicationinterface 1201 arranged for communication.

The instructions, when loaded from the memory 1205 and executed by theat least one processor 1203, may cause the first NF node 1200 to performthe method 500 for event subscription management and/or the method 800for event un-subscription management as previously discussed.

In particular, in an exemplary embodiment of the present disclosure, theinstructions, when loaded from the memory 1205 and executed by the atleast one processor 1203, may cause the first NF node 1200 to receive asubscription request of an event for a user from an event subscriber.

In response to receipt of the subscription request, the instructions,when loaded from the memory 1205 and executed by the at least oneprocessor 1203, may cause the first NF node 1200 to transmit a queryrequest for querying whether the event for the user has been subscribedto a second network function node.

The instructions, when loaded from the memory 1205 and executed by theat least one processor 1203, may cause the first NF node 1200 to receivea response to the query request from the second network function node.

If the response to the query request from the second network functionnode indicates that the event for the user has been subscribed, theinstructions, when loaded from the memory 1205 and executed by the atleast one processor 1203, may cause the first NF node 1200 to transmitan updating request to the second network function node. The updatingrequest may include identification information of the event subscriber.If the response to the query request from the second network functionnode indicates that the event for the user has not been subscribed, theinstructions, when loaded from the memory 1205 and executed by the atleast one processor 1203, may cause the first NF node 1200 to transmit,to the second network function node, a creating request withidentification information of the event subscriber for creating thesubscriber list for the event of the user, to initiate subscription ofthe event for the user with a serving node.

In another exemplary embodiment of the present disclosure, theinstructions, when loaded from the memory 1205 and executed by the atleast one processor 1203, may cause the first NF node 1200 to receive anun-subscription request of an event for a user from an event subscriber.

In response to receipt of the un-subscription request, the instructions,when loaded from the memory 1205 and executed by the at least oneprocessor 1203, may cause the first NF node 1200 to transmit to a secondnetwork function node a query request to un-subscribe the event, forquerying whether the event subscriber is a last subscriber for the eventof the user in a subscriber list of the event for the user. The queryrequest may include identification information of the event subscriber.

The instructions, when loaded from the memory 1205 and executed by theat least one processor 1203, may cause the first NF node 1200 to receivea response to the query request from the second network function node.

If the response to the query request from the second network functionnode indicates that the event subscriber is not the last subscriber forthe event of the user, the instructions, when loaded from the memory1205 and executed by the at least one processor 1203, may cause thefirst NF node 1200 to transmit, to the second network function node, aremoving request for removing, by the second network function node, theevent subscriber from the subscriber list of the event for the user.

If the response to the query request from the second network functionnode indicates that the event subscriber is the last subscriber for theevent of the user, the instructions, when loaded from the memory 1205and executed by the at least one processor 1203, may cause the first NFnode 1200 to transmit, to the second network function node, an eventremoving request to the second network function node for removing thesubscriber list by the second network function node, and to initiateun-subscription of the event for the user with a serving node.

Hereinafter, a structure of a second NF node will be described withreference to FIG. 13. FIG. 13 illustratively shows a schematic structurediagram of a second NF node 1300 (e.g. UDR 707 as shown in FIG. 7 andUDR 1007 as shown in FIG. 10, as described previously) according to anexemplary embodiment of the present disclosure. The second NF node 1300in FIG. 13 may perform the method 600 for event subscription managementdescribed previously with reference to FIG. 6 and/or the method 900 forevent un-subscription management described previously with reference toFIG. 9. Accordingly, some detailed description on the second NF node1300 may refer to the corresponding description of the method 600 forevent subscription management and/or the corresponding description ofthe method 900 for event un-subscription management as previouslydiscussed.

As shown in FIG. 13, the second NF node 1300 may include a receivingmodule 1301, a checking module 1302, a parameter updating module 1303and a transmitting module 1304. As will be understood by the skilled inthe art, common components in the second NF node 1300 are omitted inFIG. 13 for not obscuring the idea of the present disclosure. Also, somemodules may be distributed in more modules or integrated into fewermodules. For example, the receiving module 1301 and the transmittingmodule 1304 may be integrated into a transceiver module.

In an exemplary embodiment of the present disclosure, the receivingmodule 1301 of the second NF node 1300 may be configured to receive aquery request from a first network function node for querying whether anevent for a user has been subscribed. In response to reception of thequery request, the checking module 1302 of the second NF node 1300 maybe configured to check whether an indicator indicating the event for theuser has been subscribed has been set. The transmitting module 1304 ofthe second NF node 1300 may be configured to transmit a check result tothe first network function node.

In an exemplary embodiment of the present disclosure, the receivingmodule 1301 of the second NF node 1300 may be configured to receive anupdating request for updating a subscriber list of the event for theuser with an event subscriber to the event from the first networkfunction node. The updating request may include identificationinformation of the event subscriber. In response to reception of theupdating request, the parameter updating module 1303 of the second NFnode 1300 may be configured to update a subscriber list of the event forthe user to include the event subscriber.

In an exemplary embodiment of the present disclosure, the receivingmodule 1301 of the second NF node 1300 may be configured to receive acreating request with identification information of the event subscriberto subscribe the event for the user from the first network functionnode. In response to reception of the creating request, the parameterupdating module 1303 of the second NF node 1300 may be configured to setthe indicator and create the subscriber list of the event for the userand include the event subscriber into the subscriber list of the eventfor the user. In an exemplary embodiment of the present disclosure, theparameter updating module 1303 of the second NF node 1300 may beconfigured to set the indicator in a table stored in the second networkfunction node that describes event subscription of the user, and createthe subscriber list in a table stored in the second network functionnode that describes subscription of the event for the user.

In another exemplary embodiment of the present disclosure, the receivingmodule 1301 of the second NF node 1100 may be configured to receive aquery request for an event subscriber to un-subscribe an event for auser, from a first network function node for querying whether the eventsubscriber is a last subscriber for the event of the user in asubscriber list of the event for the user. The query request may includeidentification information of the event subscriber. In response toreception of the query request, the checking module 1302 of the secondNF node 1300 may be configured to check whether the event subscriber isthe last subscriber in the subscriber list of the event for the user.The transmitting module 1304 of the second NF node 1300 may beconfigured to transmit a check result to the first network functionnode.

In an exemplary embodiment of the present disclosure, the receivingmodule 1301 of the second NF node 1300 may be configured to receive aremoving request from the first network function node for removing theevent subscriber from the subscriber list of the event for the user. Inresponse to reception of the removing request, the parameter updatingmodule 1303 of the second NF node 1300 may be configured to remove theevent subscriber from the subscriber list of the event for the user.

In an exemplary embodiment of the present disclosure, the receivingmodule 1301 of the second NF node 1300 may be configured to receive anevent removing request for removing the subscriber list from the firstnetwork function node. In response to reception of the event removingrequest, the parameter updating module 1303 of the second NF node 1300may be configured to remove the subscriber list of the event for theuser. In response to reception of the event removing request, theparameter updating module 1303 of the second NF node 1300 may be furtherconfigured to remove an indicator indicating the event of the user hasbeen subscribed. In an exemplary embodiment of the present disclosure,the parameter updating module 1303 of the second NF node 1300 may beconfigured to remove the indicator from a table stored in the secondnetwork function node that describes event subscription of the user, andremove the subscriber list from a table stored in the second networkfunction node that describes subscription of the event for the user.

Hereinafter, another structure of a second NF node will be describedwith reference to FIG. 14. FIG. 14 illustratively shows a schematicstructure diagram of a second NF node 1400 (e.g., UDR 707 as shown inFIG. 7 and UDR 1007 as shown in FIG. 10, as described previously)according to an exemplary embodiment of the present disclosure. Thesecond NF node 1400 in FIG. 14 may perform the method 600 for eventsubscription management described previously with reference to FIG. 6and/or the method 900 for event un-subscription management describedpreviously with reference to FIG. 9. Accordingly, some detaileddescription on the second NF node 1400 may refer to the correspondingdescription of the method 600 for event subscription management and/orthe corresponding description of the method 900 for eventun-subscription management as previously discussed.

As shown in FIG. 14, the second NF node 1400 may include at least onecontroller or processor 1403 including e.g., any suitable CentralProcessing Unit, CPU, microcontroller, Digital Signal Processor, DSP,etc., capable of executing computer program instructions. The computerprogram instructions may be stored in a memory 1405. The memory 1405 maybe any combination of a RAM (Random Access Memory) and a ROM (Read OnlyMemory). The memory may also comprise persistent storage, which, forexample, can be any single one or combination of magnetic memory,optical memory, or solid state memory or even remotely mounted memory.The exemplary second NF node 1400 further comprises a communicationinterface 1401 arranged for communication.

The instructions, when loaded from the memory 1405 and executed by theat least one processor 1403, may cause the second NF node 1400 toperform the method 600 for event subscription management describedpreviously with reference to FIG. 6 and/or the method 900 for eventun-subscription management described previously with reference to FIG.9.

In particular, in an exemplary embodiment of the present disclosure, theinstructions, when loaded from the memory 1405 and executed by the atleast one processor 1403, may cause the second NF node 1400 to receive aquery request from a first network function node for querying whether anevent for a user has been subscribed.

In response to reception of the query request, the instructions, whenloaded from the memory 1405 and executed by the at least one processor1403, may cause the second NF node 1400 to check whether an indicatorindicating the event for the user has been subscribed has been set.

The instructions, when loaded from the memory 1405 and executed by theat least one processor 1403, may cause the second NF node 1400 totransmit a check result to the first network function node.

In an exemplary embodiment of the present disclosure, the instructions,when loaded from the memory 1405 and executed by the at least oneprocessor 1403, may cause the second NF node 1400 to receive an updatingrequest for updating a subscriber list of the event for the user with anevent subscriber to the event from the first network function node. Theupdating request may include identification information of the eventsubscriber. In response to reception of the updating request, theinstructions, when loaded from the memory 1405 and executed by the atleast one processor 1403, may cause the second NF node 1400 to update asubscriber list of the event for the user to include the eventsubscriber.

In an exemplary embodiment of the present disclosure, the instructions,when loaded from the memory 1405 and executed by the at least oneprocessor 1403, may cause the second NF node 1400 to receive a creatingrequest with identification information of the event subscriber tosubscribe the event for the user from the first network function node.In response to reception of the creating request, the instructions, whenloaded from the memory 1405 and executed by the at least one processor1403, may cause the second NF node 1400 to set the indicator and createthe subscriber list of the event for the user and include the eventsubscriber into the subscriber list of the event for the user. In anexemplary embodiment of the present disclosure, the instructions, whenloaded from the memory 1405 and executed by the at least one processor1403, may cause the second NF node 1400 to set the indicator in a tablestored in the second network function node that describes eventsubscription of the user, and create the subscriber list in a tablestored in the second network function node that describes subscriptionof the event for the user.

In another exemplary embodiment of the present disclosure, theinstructions, when loaded from the memory 1405 and executed by the atleast one processor 1403, may cause the second NF node 1400 to receive aquery request for an event subscriber to un-subscribe an event for auser, from a first network function node for querying whether the eventsubscriber is a last subscriber for the event of the user in asubscriber list of the event for the user. In response to reception ofthe query request, the instructions, when loaded from the memory 1405and executed by the at least one processor 1403, may cause the second NFnode 1400 to check whether the event subscriber is the last subscriberin the subscriber list of the event for the user. The instructions, whenloaded from the memory 1405 and executed by the at least one processor1403, may cause the second NF node 1400 to transmit a check result tothe first network function node.

In an exemplary embodiment of the present disclosure, the instructions,when loaded from the memory 1405 and executed by the at least oneprocessor 1403, may cause the second NF node 1400 to receive a removingrequest from the first network function node for removing the eventsubscriber from the subscriber list of the event for the user. Inresponse to reception of the removing request, the instructions, whenloaded from the memory 1405 and executed by the at least one processor1403, may cause the second NF node 1400 to remove the event subscriberfrom the subscriber list of the event for the user.

In an exemplary embodiment of the present disclosure, the instructions,when loaded from the memory 1405 and executed by the at least oneprocessor 1403, may cause the second NF node 1400 to receive an eventremoving request for removing the subscriber list from the first networkfunction node. In response to reception of the event removing request,the instructions, when loaded from the memory 1405 and executed by theat least one processor 1403, may cause the second NF node 1400 to removethe subscriber list of the event for the user. In response to receptionof the event removing request, the instructions, when loaded from thememory 1405 and executed by the at least one processor 1403, may causethe second NF node 1400 to remove an indicator indicating the event ofthe user has been subscribed. In an exemplary embodiment of the presentdisclosure, the instructions, when loaded from the memory 1405 andexecuted by the at least one processor 1403, may cause the second NFnode 1400 to remove the indicator from a table stored in the secondnetwork function node that describes event subscription of the user, andremove the subscriber list from a table stored in the second networkfunction node that describes subscription of the event for the user.

The foregoing description of implementations provides illustration anddescription, but is not intended to be exhaustive or to limit thedisclosure to the precise form disclosed. Modifications and variationsare possible in light of the above teachings, or may be acquired frompractice of the disclosure.

Aspects of the disclosure may also be embodied as methods and/orcomputer program products. Accordingly, the disclosure may be embodiedin hardware and/or in hardware/software (including firmware, residentsoftware, microcode, etc.). Furthermore, the embodiments may take theform of a computer program product on a computer-usable orcomputer-readable storage medium having computer-usable orcomputer-readable program code embodied in the medium for use by or inconnection with an instruction execution system. Such instructionexecution system may be implemented in a standalone or distributedmanner. The actual software code or specialized control hardware used toimplement embodiments described herein is not limiting of thedisclosure. Thus, the operation and behavior of the aspects weredescribed without reference to the specific software code, it beingunderstood that those skilled in the art will be able to design softwareand control hardware to implement the aspects based on the descriptionherein.

Furthermore, certain portions of the disclosure may be implemented as“logic” that performs one or more functions. This logic may includehardware, such as an application specific integrated circuit or fieldprogrammable gate array or a combination of hardware and software.

It should be emphasized that the term “comprises/comprising” when usedin this specification is taken to specify the presence of statedfeatures, integers, steps, components or groups but does not precludethe presence or addition of one or more other features, integers, steps,components or groups thereof.

No element, act, or instruction used in the disclosure should beconstrued as critical or essential to the disclosure unless explicitlydescribed as such. Also, as used herein, the article “a” is intended toinclude one or more items. Where only one item is intended, the term“one” or similar language is used. Further, the phrase “based on” isintended to mean “based, at least in part, on” unless explicitly statedotherwise.

The foregoing description gives only the embodiments of the presentdisclosure and is not intended to limit the present disclosure in anyway. Thus, any modification, substitution, improvement or like madewithin the spirit and principle of the present disclosure should beencompassed by the scope of the present disclosure.

1. A method implemented at a first network function node for managingevent subscription, comprising: receiving a subscription request of anevent for a user from an event subscriber, in response to receipt of thesubscription request, transmitting, to a second network function node, aquery request for querying whether the event for the user has beensubscribed; and if a response to the query request from the secondnetwork function node indicates that the event for the user has beensubscribed, transmitting, to the second network function node, anupdating request for updating a subscriber list of the event for theuser by the second network function node to include the event subscriberinto the subscriber list.
 2. The method of claim 1, further comprising:initiating subscription of the event for the user with a serving node ifthe response to the query request indicates that the event for the userhas not been subscribed; and transmitting a creating request withidentification information of the event subscriber for creating thesubscriber list for the event of the user and including the eventsubscriber in the created subscriber list by the second network node. 3.The method of claim 1 wherein the first network function node is one ofa Unified Data Management (UDM), a Network Exposure Function (NEF), andan Access and Mobility Management Function (AMF).
 4. The method of claim1, wherein the second network function node is a Unified Data Repository(UDR).
 5. A method implemented at a second network function node formanaging event subscription, comprising: receiving a query request froma first network function node for querying whether an event for a userhas been subscribed, in response to reception of the query request,checking whether an indicator indicating the event for the user has beensubscribed has been set, and transmitting a check result to the firstnetwork function node.
 6. The method of claim 5, further comprising:receiving an updating request for updating a subscriber list of theevent for the user with an event subscriber to the event from the firstnetwork function node, and in response to reception of the updatingrequest, updating a subscriber list of the event for the user to includethe event subscriber.
 7. The method of claim 5, further comprising:receiving a creating request with identification information of theevent subscriber to subscribe the event for the user from the firstnetwork function node, in response to reception of the creating request,setting the indicator; and creating the subscriber list of the event forthe user and including the event subscriber into the subscriber list ofthe event for the user.
 8. The method of claim 7, wherein the indicatoris set in a table stored in the second network function node thatdescribes event subscription of the user.
 9. The method of claim 7,wherein the subscriber list is created in a table stored in the secondnetwork function node that describes subscription of the event for theuser.
 10. The method of claim 5, wherein the first network function nodeis one of a Unified Data Management (UDM), a Network Exposure Function(NEF), and an Access and Mobility Management Function (AMF).
 11. Themethod of claim 5, wherein the second network function node is a UnifiedData Repository (UDR).
 12. A method implemented at a first networkfunction node for managing event un-subscription, comprising: receivingan un-subscription request of an event for a user from an eventsubscriber to un-subscribe the event, in response to reception of theun-subscription request, transmitting, to a second network functionnode, a query request for querying whether the event subscriber is alast subscriber for the event of the user in a subscriber list of theevent for the user; and if a response to the query request from thesecond network function node indicates that the event subscriber is notthe last subscriber for the event of the user, transmitting a removingrequest to the second network function node, for removing, by the secondnetwork function node, the event subscriber from the subscriber list ofthe event for the user.
 13. The method of claim 12, wherein the removingrequest includes identification information of the event subscriber. 14.The method of claim 12, further comprising: if the response to the queryrequest indicates that the event subscriber is the last subscriber forthe event of the user, transmitting an event removing request to thesecond network function node for removing the subscriber list by thesecond network function node; and initiating un-subscription of theevent for the user with a serving node.
 15. The method of claim 12,wherein the first network function node is one of a Unified DataManagement (UDM), a Network Exposure Function (NEF), and an Access andMobility Management Function (UDR).
 16. The method of claim 12, whereinthe second network function node is a Unified Data Repository (UDR). 17.A method implemented at a second network function node for managingevent un-subscription, comprising: receiving a query request for anevent subscriber to un-subscribe an event for a user, from a firstnetwork function node for querying whether the event subscriber is alast subscriber for the event of the user in a subscriber list of theevent for the user, in response to reception of the query request,checking whether the event subscriber is the last subscriber in thesubscriber list of the event for the user, and transmitting a checkresult to the first network function node.
 18. The method of claim 17,further comprising: receiving a removing request from the first networkfunction node for removing the event subscriber from the subscriber listof the event for the user, and in response to reception of the removingrequest, removing the event subscriber from the subscriber list of theevent for the user.
 19. The method of claim 18, wherein the removingrequest includes identification information of the event subscriber toun-subscribe the event.
 20. The method of claim 17, further comprising:receiving an event removing request for removing the subscriber listfrom the first network function node, and in response to reception ofthe event removing request, removing the subscriber list of the eventfor the user.
 21. The method of claim 20, further comprising: removingan indicator indicating the event of the user has been subscribed. 22.The method of claim 20, wherein the removing the subscriber listcomprises removing the subscriber list from a table stored in the secondnetwork function node that describes subscription of the event for theuser.
 23. The method of claim 21, wherein the removing the indicatorcomprises removing the indicator from a table stored in the secondnetwork function node that describes event subscription of the user.24.-28. (canceled)